HP Support Assistant is the oft-default tool, not suitable for automation. It does work, but often misses items, and sometimes just generally coughs. There is also the HP Image Assistant:

ftp.ext.hp.com/pub/caps-softpaq/cmit/HPIA.html

Its primary purpose is maintaining reference images, but it has a great command-line mode for full automatic downloads and updates. Download the installer, complete it, close the GUI tool, open Powershell or CMD, CD to the folder it created in command-line (it’s C:\SWSETUP\something), and run:

.\HPImageAssistant /Operation:Analyze /Category:All,Accessories /selection:All /action:Install /silent /reportFolder:c:\HPIA\Report /softpaqdownloadfolder:c:\HPIA\download

Then monitor its behavior in TASKMGR, and see the downloads piling up in C:\HPIA\download. If it needs a reboot, it will do it automatically. Even if it doesn’t, reboot is recommended, just to keep everything as smooth as possible.